- Light duration. Daily sessions of 20 to 60 minutes may be needed. Since light intensity and duration interact, longer sessions will be needed at lower intensities. At 10,000 lux – the current standard – 30-minute sessions are most typical.
- Time of Day of exposure. The antidepressant effect, many investigators think, is mediated by light’s action on the internal circadian rhythm clock. Most patients with winter depression benefit by resetting this clock earlier, which is achieved specifically with morning light exposure. Since different people have different clock phases (early types, neutral types, late types), the optimum time of light exposure can differ greatly. The Center for Environmental Therapeutics, a professional nonprofit agency, offers an on-line questionnaire on its website, www.cet.org, which can be used to calculate a recommended treatment time individually, which is then adjusted depending on response. Long sleepers may need to wake up earlier for best effect, while short sleepers can maintain their habitual sleep-wake schedule.
Side effects of light therapy are uncommon. Some patients complain of irritability, eyestrain, headaches, or nausea. Those who have histories of hypomania in spring or summer are at risk for switching states under light therapy, in which case light dose needs to be reduced. There is no evidence for long-term adverse effects, however, and disturbances experienced during the first few exposures often disappear spontaneously. As an important precaution, patients with Bipolar I disorder – who are at risk for switching into full-blown manic episodes – need to be on a mood-stabilizing drug while using light therapy.
What should I do if I think I have SAD?
If your symptoms are mild – that is, if they don't interfere too much with your daily living, you may want to try light therapy as described above or experiment with adjusting the light in your surroundings with bright lamps and scheduling more time outdoors in winter.
If your depressive symptoms are severe enough to significantly affect your daily living, consult a mental health professional qualified to treat SAD. He or she can help you find the most appropriate treatment for you. To help you decide whether a clinical consultation is necessary, you can use the feedback on the Personalized Inventory for Depression and SAD at www.cet.org.
Reviewed by Michael Terman, Ph.D., Director, Winter Depression Program, New York State Psychiatric Institute at Columbia University Medical Center. New York City (February, 2004).
Reprinted with permission from the National Alliance on Mental Illness (NAMI), www.nami.org.
